Transcutaneous energy transfer (TET) systems are used to supply power to devices such as pumps implanted internally within a human body. A magnetic field generated by a transmitting coil outside the body can transmit power across a cutaneous (skin) barrier to a magnetic receiving coil implanted within the body. The receiving coil can then transfer the received power to the implanted pump or other internal device and to one or more batteries implanted within the body to charge the battery.
Such systems should efficiently generate and wirelessly transmit a sufficient amount of energy to power one or more implanted devices while maintaining the system's efficiency, safety, and overall convenience of use.
With respect to those systems' efficiency, one drawback suffered by present TET systems arises from the nature of the magnetic field generated by the transmitting coil. By its nature, the field extends from the transmitting coil in every direction. As such, much of the energy from the electromagnetic field emitted by the transmitting coil is not focused effectively or optimally at the receiving coil. This limits the efficiency (i.e., the coupling coefficient) of the wireless energy transfer. Another challenge arises from the fact that power and/or current demands of an implanted device are not constant but rather subject to vary. As such, there is a need to efficiently accommodate such changes in power and/or current demand in order to most effectively power the implanted device.
With respect to convenience of the system, one challenge among present TET systems arises from the difficulty in maintaining optimal axial alignment (in proximity to the surface of the patient's skin) and radial alignment (across the surface of the patient's skin) between the transmitting and receiving coils to increase power transfer efficiency and minimize transmitting coil losses that would result in heating. Firstly, a transmitting coil worn on the exterior of the body is subject to shift in position, such as due to movement by the wearer. Moreover, once the transmitting coil is shifted out of place, repositioning the coil, such as determining in which direction to move the coil in order to reestablish alignment, may be difficult without some form of guidance. As such, there is a need for a system that assists the wearer in positioning or repositioning the transmitting coil.
Further, a shift in the position of a transmitting coil worn on the exterior of the body also poses issues with respect to health and safety of the system's wearer. If the coil shifts out of its proper alignment while operating at full power, not only may the coupling coefficient of the power transfer be reduced, but it may cause unwanted overheating to the wearer, and such overheating may be harmful to the skin or surrounding tissue.